1. Field of the Invention
This invention relates generally to environmental protection for electronic components, and more particularly it pertains to a method and apparatus for packaging electronic components such as for example pulse transformers or the like with a thermosetting material.
2. Description of the Prior Art
Pulse transformers, which find extensive use in the fields of electronic computers, communications equipment and so forth, are required to have a high reliability permanently. In order to meet such a requirement, various methods have already been proposed, among which is a method of encapsulating pulse transformer elements with a thermosetting material such as a phenolic or epoxy resin. Such pulse transformer elements comprise a toroidal core having coils wound thereon and embedded in a plate-like base member of an insulating material which is provided at opposite sides thereof with a plurality of terminal pins extending vertically therethrough, with the upper ends of which are connected the ends of the aforementioned coils.
In the conventional method, use is made of a molding cavity defined by upper and lower molds having discrete holes about 0.5 to 1.2 mm in diameter formed in the bottom surface thereof, and the terminal pins of the pulse transformer elements are inserted into the holes of the molding cavity prior to molding operation. Obviously, this prior art technique has disadvantages. It is very tedious and inefficient to insert the terminal pins into the cavity holes individually. In addition, it is inevitable that a thermosetting material injected into the molding cavity is caused to enter the holes mentioned above and adhere to the terminal pins so that flashes are caused to occur not only between the upper and lower molds but also at the terminal pins of the encapsulated pulse transformer elements. After the molding operation is completed, such flashes must be removed from the finished products. Apparently, this not only lowers the efficiency of operation but also leads to a poor yield since it is very likely that during the removal of the flashes, the finished products are damaged so that their appearance is deteriorated or in the worst case they become unmarketable. Furthermore, forming the discrete holes, which are required to have a precise dimension, in the cavity surface, makes the molds per se expensive.